<?php
#
# Markdown  -  A text-to-HTML conversion tool for web writers
#
# PHP Markdown
# Copyright (c) 2004-2013 Michel Fortin
# <http://michelf.com/projects/php-markdown/>
#
# Original Markdown
# Copyright (c) 2004-2006 John Gruber
# <http://daringfireball.net/projects/markdown/>
#

# 应用到ThinkPHP中，因而修改为ThinkPHP规范的命名空间
# namespace Michelf;
namespace org\parser\driver;

#
# The following two constants are deprecated: avoid using them, they'll
# disappear when the Lib branch becomes the only one to be updated.
#
# You can get the parser's version using the constant inside of the parser
# class: \Michelf\Markdown::MARKDOWNLIB_VERSION.
#

const MARKDOWN_VERSION      = "1.0.1p"; # Sun 13 Jan 2013
const MARKDOWNEXTRA_VERSION = "1.2.6"; # Sun 13 Jan 2013

#
# Markdown Parser Class
#

class Markdown
{

    ### Version ###

    const MARKDOWNLIB_VERSION = "1.3-beta4";

    ### Simple Function Interface ###

    public static function defaultTransform($text)
    {
        #
        # Initialize the parser and return the result of its transform method.
        # This will work fine for derived classes too.
        #
        # Take parser class on which this function was called.
        $parser_class = \get_called_class();

        # try to take parser from the static parser list
        static $parser_list;
        $parser = &$parser_list[$parser_class];

        # create the parser it not already set
        if (!$parser) {
            $parser = new $parser_class;
        }

        # Transform text using parser.
        return $parser->transform($text);
    }

    ### Configuration Variables ###

    # Change to ">" for HTML output.
    public $empty_element_suffix = " />";
    public $tab_width            = 4;

    # Change to `true` to disallow markup or entities.
    public $no_markup   = false;
    public $no_entities = false;

    # Predefined urls and titles for reference links and images.
    public $predef_urls   = array();
    public $predef_titles = array();

    ### Parser Implementation ###

    # Regex to match balanced [brackets].
    # Needed to insert a maximum bracked depth while converting to PHP.
    protected $nested_brackets_depth = 6;
    protected $nested_brackets_re;

    protected $nested_url_parenthesis_depth = 4;
    protected $nested_url_parenthesis_re;

    # Table of hash values for escaped characters:
    protected $escape_chars = '\`*_{}[]()>#+-.!';
    protected $escape_chars_re;

    public function __construct()
    {
        #
        # Constructor function. Initialize appropriate member variables.
        #
        $this->_initDetab();
        $this->prepareItalicsAndBold();

        $this->nested_brackets_re =
        str_repeat('(?>[^\[\]]+|\[', $this->nested_brackets_depth) .
        str_repeat('\])*', $this->nested_brackets_depth);

        $this->nested_url_parenthesis_re =
        str_repeat('(?>[^()\s]+|\(', $this->nested_url_parenthesis_depth) .
        str_repeat('(?>\)))*', $this->nested_url_parenthesis_depth);

        $this->escape_chars_re = '[' . preg_quote($this->escape_chars) . ']';

        # Sort document, block, and span gamut in ascendent priority order.
        asort($this->document_gamut);
        asort($this->block_gamut);
        asort($this->span_gamut);
    }

    # Internal hashes used during transformation.
    protected $urls        = array();
    protected $titles      = array();
    protected $html_hashes = array();

    # Status flag to avoid invalid nesting.
    protected $in_anchor = false;

    protected function setup()
    {
        #
        # Called before the transformation process starts to setup parser
        # states.
        #
        # Clear global hashes.
        $this->urls        = $this->predef_urls;
        $this->titles      = $this->predef_titles;
        $this->html_hashes = array();

        $this->in_anchor = false;
    }

    protected function teardown()
    {
        #
        # Called after the transformation process to clear any variable
        # which may be taking up memory unnecessarly.
        #
        $this->urls        = array();
        $this->titles      = array();
        $this->html_hashes = array();
    }

    /**
     * 提供给ThinkPHP外部调用的方法，麦当苗儿为ThinkPHP添加
     * @author <zuojiazi.cn@gmail.com>
     * @param  string $content 需要解析的Markdown字符串
     * @return string          解析后的HTML字符串
     */
    public function parse($content)
    {
        return $this->transform($content);
    }

    protected function transform($text)
    {
        #
        # Main function. Performs some preprocessing on the input text
        # and pass it through the document gamut.
        #
        $this->setup();

        # Remove UTF-8 BOM and marker character in input, if present.
        $text = preg_replace('{^\xEF\xBB\xBF|\x1A}', '', $text);

        # Standardize line endings:
        #   DOS to Unix and Mac to Unix
        $text = preg_replace('{\r\n?}', "\n", $text);

        # Make sure $text ends with a couple of newlines:
        $text .= "\n\n";

        # Convert all tabs to spaces.
        $text = $this->detab($text);

        # Turn block-level HTML blocks into hash entries
        $text = $this->hashHTMLBlocks($text);

        # Strip any lines consisting only of spaces and tabs.
        # This makes subsequent regexen easier to write, because we can
        # match consecutive blank lines with /\n+/ instead of something
        # contorted like /[ ]*\n+/ .
        $text = preg_replace('/^[ ]+$/m', '', $text);

        # Run document gamut methods.
        foreach ($this->document_gamut as $method => $priority) {
            $text = $this->$method($text);
        }

        $this->teardown();

        return $text . "\n";
    }

    protected $document_gamut = array(
        # Strip link definitions, store in hashes.
        "stripLinkDefinitions" => 20,

        "runBasicBlockGamut"   => 30,
    );

    protected function stripLinkDefinitions($text)
    {
        #
        # Strips link definitions from text, stores the URLs and titles in
        # hash references.
        #
        $less_than_tab = $this->tab_width - 1;

        # Link defs are in the form: ^[id]: url "optional title"
        $text = preg_replace_callback('{
							^[ ]{0,' . $less_than_tab . '}\[(.+)\][ ]?:	# id = $1
							  [ ]*
							  \n?				# maybe *one* newline
							  [ ]*
							(?:
							  <(.+?)>			# url = $2
							|
							  (\S+?)			# url = $3
							)
							  [ ]*
							  \n?				# maybe one newline
							  [ ]*
							(?:
								(?<=\s)			# lookbehind for whitespace
								["(]
								(.*?)			# title = $4
								[")]
								[ ]*
							)?	# title is optional
							(?:\n+|\Z)
			}xm',
            array(&$this, '_stripLinkDefinitions_callback'),
            $text);
        return $text;
    }
    protected function _stripLinkDefinitions_callback($matches)
    {
        $link_id                = strtolower($matches[1]);
        $url                    = '' == $matches[2] ? $matches[3] : $matches[2];
        $this->urls[$link_id]   = $url;
        $this->titles[$link_id] = &$matches[4];
        return ''; # String that will replace the block
    }

    protected function hashHTMLBlocks($text)
    {
        if ($this->no_markup) {
            return $text;
        }

        $less_than_tab = $this->tab_width - 1;

        # Hashify HTML blocks:
        # We only want to do this for block-level HTML tags, such as headers,
        # lists, and tables. That's because we still want to wrap <p>s around
        # "paragraphs" that are wrapped in non-block-level tags, such as anchors,
        # phrase emphasis, and spans. The list of tags we're looking for is
        # hard-coded:
        #
        # *  List "a" is made of tags which can be both inline or block-level.
        #    These will be treated block-level when the start tag is alone on
        #    its line, otherwise they're not matched here and will be taken as
        #    inline later.
        # *  List "b" is made of tags which are always block-level;
        #
        $block_tags_a_re = 'ins|del';
        $block_tags_b_re = 'p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|address|' .
        'script|noscript|form|fieldset|iframe|math|svg|' .
        'article|section|nav|aside|hgroup|header|footer|' .
        'figure';

        # Regular expression for the content of a block tag.
        $nested_tags_level = 4;
        $attr              = '
			(?>				# optional tag attributes
			  \s			# starts with whitespace
			  (?>
				[^>"/]+		# text outside quotes
			  |
				/+(?!>)		# slash not followed by ">"
			  |
				"[^"]*"		# text inside double quotes (tolerate ">")
			  |
				\'[^\']*\'	# text inside single quotes (tolerate ">")
			  )*
			)?
			';
        $content =
        str_repeat('
				(?>
				  [^<]+			# content without tag
				|
				  <\2			# nested opening tag
					' . $attr . '	# attributes
					(?>
					  />
					|
					  >', $nested_tags_level) . # end of opening tag
        '.*?' . # last level nested tag content
        str_repeat('
					  </\2\s*>	# closing nested tag
					)
				  |
					<(?!/\2\s*>	# other tags with a different name
				  )
				)*',
            $nested_tags_level);
        $content2 = str_replace('\2', '\3', $content);

        # First, look for nested blocks, e.g.:
        #     <div>
        #         <div>
        #         tags for inner block must be indented.
        #         </div>
        #     </div>
        #
        # The outermost tags must start at the left margin for this to match, and
        # the inner nested divs must be indented.
        # We need to do this before the next, more liberal match, because the next
        # match will start at the first `<div>` and stop at the first `</div>`.
        $text = preg_replace_callback('{(?>
			(?>
				(?<=\n\n)		# Starting after a blank line
				|				# or
				\A\n?			# the beginning of the doc
			)
			(						# save in $1

			  # Match from `\n<tag>` to `</tag>\n`, handling nested tags
			  # in between.

						[ ]{0,' . $less_than_tab . '}
						<(' . $block_tags_b_re . ')# start tag = $2
						' . $attr . '>			# attributes followed by > and \n
						' . $content . '		# content, support nesting
						</\2>				# the matching end tag
						[ ]*				# trailing spaces/tabs
						(?=\n+|\Z)	# followed by a newline or end of document

			| # Special version for tags of group a.

						[ ]{0,' . $less_than_tab . '}
						<(' . $block_tags_a_re . ')# start tag = $3
						' . $attr . '>[ ]*\n	# attributes followed by >
						' . $content2 . '		# content, support nesting
						</\3>				# the matching end tag
						[ ]*				# trailing spaces/tabs
						(?=\n+|\Z)	# followed by a newline or end of document

			| # Special case just for <hr />. It was easier to make a special
			  # case than to make the other regex more complicated.

						[ ]{0,' . $less_than_tab . '}
						<(hr)				# start tag = $2
						' . $attr . '			# attributes
						/?>					# the matching end tag
						[ ]*
						(?=\n{2,}|\Z)		# followed by a blank line or end of document

			| # Special case for standalone HTML comments:

					[ ]{0,' . $less_than_tab . '}
					(?s:
						<!-- .*? -->
					)
					[ ]*
					(?=\n{2,}|\Z)		# followed by a blank line or end of document

			| # PHP and ASP-style processor instructions (<? and <%)

					[ ]{0,' . $less_than_tab . '}
					(?s:
						<([?%])			# $2
						.*?
						\2>
					)
					[ ]*
					(?=\n{2,}|\Z)		# followed by a blank line or end of document

			)
			)}Sxmi',
            array(&$this, '_hashHTMLBlocks_callback'),
            $text);

        return $text;
    }
    protected function _hashHTMLBlocks_callback($matches)
    {
        $text = $matches[1];
        $key  = $this->hashBlock($text);
        return "\n\n$key\n\n";
    }

    protected function hashPart($text, $boundary = 'X')
    {
        #
        # Called whenever a tag must be hashed when a function insert an atomic
        # element in the text stream. Passing $text to through this function gives
        # a unique text-token which will be reverted back when calling unhash.
        #
        # The $boundary argument specify what character should be used to surround
        # the token. By convension, "B" is used for block elements that needs not
        # to be wrapped into paragraph tags at the end, ":" is used for elements
        # that are word separators and "X" is used in the general case.
        #
        # Swap back any tag hash found in $text so we do not have to `unhash`
        # multiple times at the end.
        $text = $this->unhash($text);

        # Then hash the block.
        static $i                = 0;
        $key                     = "$boundary\x1A" . ++$i . $boundary;
        $this->html_hashes[$key] = $text;
        return $key; # String that will replace the tag.
    }

    protected function hashBlock($text)
    {
        #
        # Shortcut function for hashPart with block-level boundaries.
        #
        return $this->hashPart($text, 'B');
    }

    protected $block_gamut = array(
        #
        # These are all the transformations that form block-level
        # tags like paragraphs, headers, and list items.
        #
        "doHeaders"         => 10,
        "doHorizontalRules" => 20,

        "doLists"           => 40,
        "doCodeBlocks"      => 50,
        "doBlockQuotes"     => 60,
    );

    protected function runBlockGamut($text)
    {
        #
        # Run block gamut tranformations.
        #
        # We need to escape raw HTML in Markdown source before doing anything
        # else. This need to be done for each block, and not only at the
        # begining in the Markdown function since hashed blocks can be part of
        # list items and could have been indented. Indented blocks would have
        # been seen as a code block in a previous pass of hashHTMLBlocks.
        $text = $this->hashHTMLBlocks($text);

        return $this->runBasicBlockGamut($text);
    }

    protected function runBasicBlockGamut($text)
    {
        #
        # Run block gamut tranformations, without hashing HTML blocks. This is
        # useful when HTML blocks are known to be already hashed, like in the first
        # whole-document pass.
        #
        foreach ($this->block_gamut as $method => $priority) {
            $text = $this->$method($text);
        }

        # Finally form paragraph and restore hashed blocks.
        $text = $this->formParagraphs($text);

        return $text;
    }

    protected function doHorizontalRules($text)
    {
        # Do Horizontal Rules:
        return preg_replace(
            '{
				^[ ]{0,3}	# Leading space
				([-*_])		# $1: First marker
				(?>			# Repeated marker group
					[ ]{0,2}	# Zero, one, or two spaces.
					\1			# Marker character
				){2,}		# Group repeated at least twice
				[ ]*		# Tailing spaces
				$			# End of line.
			}mx',
            "\n" . $this->hashBlock("<hr$this->empty_element_suffix") . "\n",
            $text);
    }

    protected $span_gamut = array(
        #
        # These are all the transformations that occur *within* block-level
        # tags like paragraphs, headers, and list items.
        #
        # Process character escapes, code spans, and inline HTML
        # in one shot.
        "parseSpan"           => -30,

        # Process anchor and image tags. Images must come first,
        # because ![foo][f] looks like an anchor.
        "doImages"            => 10,
        "doAnchors"           => 20,

        # Make links out of things like `<http://example.com/>`
        # Must come after doAnchors, because you can use < and >
        # delimiters in inline links like [this](<url>).
        "doAutoLinks"         => 30,
        "encodeAmpsAndAngles" => 40,

        "doItalicsAndBold"    => 50,
        "doHardBreaks"        => 60,
    );

    protected function runSpanGamut($text)
    {
        #
        # Run span gamut tranformations.
        #
        foreach ($this->span_gamut as $method => $priority) {
            $text = $this->$method($text);
        }

        return $text;
    }

    protected function doHardBreaks($text)
    {
        # Do hard breaks:
        return preg_replace_callback('/ {2,}\n/',
            array(&$this, '_doHardBreaks_callback'), $text);
    }
    protected function _doHardBreaks_callback($matches)
    {
        return $this->hashPart("<br$this->empty_element_suffix\n");
    }

    protected function doAnchors($text)
    {
        #
        # Turn Markdown link shortcuts into XHTML <a> tags.
        #
        if ($this->in_anchor) {
            return $text;
        }

        $this->in_anchor = true;

        #
        # First, handle reference-style links: [link text] [id]
        #
        $text = preg_replace_callback('{
			(					# wrap whole match in $1
			  \[
				(' . $this->nested_brackets_re . ')	# link text = $2
			  \]

			  [ ]?				# one optional space
			  (?:\n[ ]*)?		# one optional newline followed by spaces

			  \[
				(.*?)		# id = $3
			  \]
			)
			}xs',
            array(&$this, '_doAnchors_reference_callback'), $text);

        #
        # Next, inline-style links: [link text](url "optional title")
        #
        $text = preg_replace_callback('{
			(				# wrap whole match in $1
			  \[
				(' . $this->nested_brackets_re . ')	# link text = $2
			  \]
			  \(			# literal paren
				[ \n]*
				(?:
					<(.+?)>	# href = $3
				|
					(' . $this->nested_url_parenthesis_re . ')	# href = $4
				)
				[ \n]*
				(			# $5
				  ([\'"])	# quote char = $6
				  (.*?)		# Title = $7
				  \6		# matching quote
				  [ \n]*	# ignore any spaces/tabs between closing quote and )
				)?			# title is optional
			  \)
			)
			}xs',
            array(&$this, '_doAnchors_inline_callback'), $text);

        #
        # Last, handle reference-style shortcuts: [link text]
        # These must come last in case you've also got [link text][1]
        # or [link text](/foo)
        #
        $text = preg_replace_callback('{
			(					# wrap whole match in $1
			  \[
				([^\[\]]+)		# link text = $2; can\'t contain [ or ]
			  \]
			)
			}xs',
            array(&$this, '_doAnchors_reference_callback'), $text);

        $this->in_anchor = false;
        return $text;
    }
    protected function _doAnchors_reference_callback($matches)
    {
        $whole_match = $matches[1];
        $link_text   = $matches[2];
        $link_id     = &$matches[3];

        if ("" == $link_id) {
            # for shortcut links like [this][] or [this].
            $link_id = $link_text;
        }

        # lower-case and turn embedded newlines into spaces
        $link_id = strtolower($link_id);
        $link_id = preg_replace('{[ ]?\n}', ' ', $link_id);

        if (isset($this->urls[$link_id])) {
            $url = $this->urls[$link_id];
            $url = $this->encodeAttribute($url);

            $result = "<a href=\"$url\"";
            if (isset($this->titles[$link_id])) {
                $title = $this->titles[$link_id];
                $title = $this->encodeAttribute($title);
                $result .= " title=\"$title\"";
            }

            $link_text = $this->runSpanGamut($link_text);
            $result .= ">$link_text</a>";
            $result = $this->hashPart($result);
        } else {
            $result = $whole_match;
        }
        return $result;
    }
    protected function _doAnchors_inline_callback($matches)
    {
        $whole_match = $matches[1];
        $link_text   = $this->runSpanGamut($matches[2]);
        $url         = '' == $matches[3] ? $matches[4] : $matches[3];
        $title       = &$matches[7];

        $url = $this->encodeAttribute($url);

        $result = "<a href=\"$url\"";
        if (isset($title)) {
            $title = $this->encodeAttribute($title);
            $result .= " title=\"$title\"";
        }

        $link_text = $this->runSpanGamut($link_text);
        $result .= ">$link_text</a>";

        return $this->hashPart($result);
    }

    protected function doImages($text)
    {
        #
        # Turn Markdown image shortcuts into <img> tags.
        #
        #
        # First, handle reference-style labeled images: ![alt text][id]
        #
        $text = preg_replace_callback('{
			(				# wrap whole match in $1
			  !\[
				(' . $this->nested_brackets_re . ')		# alt text = $2
			  \]

			  [ ]?				# one optional space
			  (?:\n[ ]*)?		# one optional newline followed by spaces

			  \[
				(.*?)		# id = $3
			  \]

			)
			}xs',
            array(&$this, '_doImages_reference_callback'), $text);

        #
        # Next, handle inline images:  ![alt text](url "optional title")
        # Don't forget: encode * and _
        #
        $text = preg_replace_callback('{
			(				# wrap whole match in $1
			  !\[
				(' . $this->nested_brackets_re . ')		# alt text = $2
			  \]
			  \s?			# One optional whitespace character
			  \(			# literal paren
				[ \n]*
				(?:
					<(\S*)>	# src url = $3
				|
					(' . $this->nested_url_parenthesis_re . ')	# src url = $4
				)
				[ \n]*
				(			# $5
				  ([\'"])	# quote char = $6
				  (.*?)		# title = $7
				  \6		# matching quote
				  [ \n]*
				)?			# title is optional
			  \)
			)
			}xs',
            array(&$this, '_doImages_inline_callback'), $text);

        return $text;
    }
    protected function _doImages_reference_callback($matches)
    {
        $whole_match = $matches[1];
        $alt_text    = $matches[2];
        $link_id     = strtolower($matches[3]);

        if ("" == $link_id) {
            $link_id = strtolower($alt_text); # for shortcut links like ![this][].
        }

        $alt_text = $this->encodeAttribute($alt_text);
        if (isset($this->urls[$link_id])) {
            $url    = $this->encodeAttribute($this->urls[$link_id]);
            $result = "<img src=\"$url\" alt=\"$alt_text\"";
            if (isset($this->titles[$link_id])) {
                $title = $this->titles[$link_id];
                $title = $this->encodeAttribute($title);
                $result .= " title=\"$title\"";
            }
            $result .= $this->empty_element_suffix;
            $result = $this->hashPart($result);
        } else {
            # If there's no such link ID, leave intact:
            $result = $whole_match;
        }

        return $result;
    }
    protected function _doImages_inline_callback($matches)
    {
        $whole_match = $matches[1];
        $alt_text    = $matches[2];
        $url         = '' == $matches[3] ? $matches[4] : $matches[3];
        $title       = &$matches[7];

        $alt_text = $this->encodeAttribute($alt_text);
        $url      = $this->encodeAttribute($url);
        $result   = "<img src=\"$url\" alt=\"$alt_text\"";
        if (isset($title)) {
            $title = $this->encodeAttribute($title);
            $result .= " title=\"$title\""; # $title already quoted
        }
        $result .= $this->empty_element_suffix;

        return $this->hashPart($result);
    }

    protected function doHeaders($text)
    {
        # Setext-style headers:
        #      Header 1
        #      ========
        #
        #      Header 2
        #      --------
        #
        $text = preg_replace_callback('{ ^(.+?)[ ]*\n(=+|-+)[ ]*\n+ }mx',
            array(&$this, '_doHeaders_callback_setext'), $text);

        # atx-style headers:
        #    # Header 1
        #    ## Header 2
        #    ## Header 2 with closing hashes ##
        #    ...
        #    ###### Header 6
        #
        $text = preg_replace_callback('{
				^(\#{1,6})	# $1 = string of #\'s
				[ ]*
				(.+?)		# $2 = Header text
				[ ]*
				\#*			# optional closing #\'s (not counted)
				\n+
			}xm',
            array(&$this, '_doHeaders_callback_atx'), $text);

        return $text;
    }
    protected function _doHeaders_callback_setext($matches)
    {
        # Terrible hack to check we haven't found an empty list item.
        if ('-' == $matches[2] && preg_match('{^-(?: |$)}', $matches[1])) {
            return $matches[0];
        }

        $level = '=' == $matches[2]{0} ? 1 : 2;
        $block = "<h$level>" . $this->runSpanGamut($matches[1]) . "</h$level>";
        return "\n" . $this->hashBlock($block) . "\n\n";
    }
    protected function _doHeaders_callback_atx($matches)
    {
        $level = strlen($matches[1]);
        $block = "<h$level>" . $this->runSpanGamut($matches[2]) . "</h$level>";
        return "\n" . $this->hashBlock($block) . "\n\n";
    }

    protected function doLists($text)
    {
        #
        # Form HTML ordered (numbered) and unordered (bulleted) lists.
        #
        $less_than_tab = $this->tab_width - 1;

        # Re-usable patterns to match list item bullets and number markers:
        $marker_ul_re  = '[*+-]';
        $marker_ol_re  = '\d+[\.]';
        $marker_any_re = "(?:$marker_ul_re|$marker_ol_re)";

        $markers_relist = array(
            $marker_ul_re => $marker_ol_re,
            $marker_ol_re => $marker_ul_re,
        );

        foreach ($markers_relist as $marker_re => $other_marker_re) {
            # Re-usable pattern to match any entirel ul or ol list:
            $whole_list_re = '
				(								# $1 = whole list
				  (								# $2
					([ ]{0,' . $less_than_tab . '})	# $3 = number of spaces
					(' . $marker_re . ')			# $4 = first list item marker
					[ ]+
				  )
				  (?s:.+?)
				  (								# $5
					  \z
					|
					  \n{2,}
					  (?=\S)
					  (?!						# Negative lookahead for another list item marker
						[ ]*
						' . $marker_re . '[ ]+
					  )
					|
					  (?=						# Lookahead for another kind of list
					    \n
						\3						# Must have the same indentation
						' . $other_marker_re . '[ ]+
					  )
				  )
				)
			'; // mx

            # We use a different prefix before nested lists than top-level lists.
            # See extended comment in _ProcessListItems().

            if ($this->list_level) {
                $text = preg_replace_callback('{
						^
						' . $whole_list_re . '
					}mx',
                    array(&$this, '_doLists_callback'), $text);
            } else {
                $text = preg_replace_callback('{
						(?:(?<=\n)\n|\A\n?) # Must eat the newline
						' . $whole_list_re . '
					}mx',
                    array(&$this, '_doLists_callback'), $text);
            }
        }

        return $text;
    }
    protected function _doLists_callback($matches)
    {
        # Re-usable patterns to match list item bullets and number markers:
        $marker_ul_re  = '[*+-]';
        $marker_ol_re  = '\d+[\.]';
        $marker_any_re = "(?:$marker_ul_re|$marker_ol_re)";

        $list      = $matches[1];
        $list_type = preg_match("/$marker_ul_re/", $matches[4]) ? "ul" : "ol";

        $marker_any_re = ("ul" == $list_type ? $marker_ul_re : $marker_ol_re);

        $list .= "\n";
        $result = $this->processListItems($list, $marker_any_re);

        $result = $this->hashBlock("<$list_type>\n" . $result . "</$list_type>");
        return "\n" . $result . "\n\n";
    }

    protected $list_level = 0;

    protected function processListItems($list_str, $marker_any_re)
    {
        #
        #    Process the contents of a single ordered or unordered list, splitting it
        #    into individual list items.
        #
        # The $this->list_level global keeps track of when we're inside a list.
        # Each time we enter a list, we increment it; when we leave a list,
        # we decrement. If it's zero, we're not in a list anymore.
        #
        # We do this because when we're not inside a list, we want to treat
        # something like this:
        #
        #        I recommend upgrading to version
        #        8. Oops, now this line is treated
        #        as a sub-list.
        #
        # As a single paragraph, despite the fact that the second line starts
        # with a digit-period-space sequence.
        #
        # Whereas when we're inside a list (or sub-list), that line will be
        # treated as the start of a sub-list. What a kludge, huh? This is
        # an aspect of Markdown's syntax that's hard to parse perfectly
        # without resorting to mind-reading. Perhaps the solution is to
        # change the syntax rules such that sub-lists must start with a
        # starting cardinal number; e.g. "1." or "a.".

        $this->list_level++;

        # trim trailing blank lines:
        $list_str = preg_replace("/\n{2,}\\z/", "\n", $list_str);

        $list_str = preg_replace_callback('{
			(\n)?							# leading line = $1
			(^[ ]*)							# leading whitespace = $2
			(' . $marker_any_re . '				# list marker and space = $3
				(?:[ ]+|(?=\n))	# space only required if item is not empty
			)
			((?s:.*?))						# list item text   = $4
			(?:(\n+(?=\n))|\n)				# tailing blank line = $5
			(?= \n* (\z | \2 (' . $marker_any_re . ') (?:[ ]+|(?=\n))))
			}xm',
            array(&$this, '_processListItems_callback'), $list_str);

        $this->list_level--;
        return $list_str;
    }
    protected function _processListItems_callback($matches)
    {
        $item               = $matches[4];
        $leading_line       = &$matches[1];
        $leading_space      = &$matches[2];
        $marker_space       = $matches[3];
        $tailing_blank_line = &$matches[5];

        if ($leading_line || $tailing_blank_line ||
            preg_match('/\n{2,}/', $item)) {
            # Replace marker with the appropriate whitespace indentation
            $item = $leading_space . str_repeat(' ', strlen($marker_space)) . $item;
            $item = $this->runBlockGamut($this->outdent($item) . "\n");
        } else {
            # Recursion for sub-lists:
            $item = $this->doLists($this->outdent($item));
            $item = preg_replace('/\n+$/', '', $item);
            $item = $this->runSpanGamut($item);
        }

        return "<li>" . $item . "</li>\n";
    }

    protected function doCodeBlocks($text)
    {
        #
        #    Process Markdown `<pre><code>` blocks.
        #
        $text = preg_replace_callback('{
				(?:\n\n|\A\n?)
				(	            # $1 = the code block -- one or more lines, starting with a space/tab
				  (?>
					[ ]{' . $this->tab_width . '}  # Lines must start with a tab or a tab-width of spaces
					.*\n+
				  )+
				)
				((?=^[ ]{0,' . $this->tab_width . '}\S)|\Z)	# Lookahead for non-space at line-start, or end of doc
			}xm',
            array(&$this, '_doCodeBlocks_callback'), $text);

        return $text;
    }
    protected function _doCodeBlocks_callback($matches)
    {
        $codeblock = $matches[1];

        $codeblock = $this->outdent($codeblock);
        $codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);

        # trim leading newlines and trailing newlines
        $codeblock = preg_replace('/\A\n+|\n+\z/', '', $codeblock);

        $codeblock = "<pre><code>$codeblock\n</code></pre>";
        return "\n\n" . $this->hashBlock($codeblock) . "\n\n";
    }

    protected function makeCodeSpan($code)
    {
        #
        # Create a code span markup for $code. Called from handleSpanToken.
        #
        $code = htmlspecialchars(trim($code), ENT_NOQUOTES);
        return $this->hashPart("<code>$code</code>");
    }

    protected $em_relist = array(
        ''  => '(?:(?<!\*)\*(?!\*)|(?<!_)_(?!_))(?=\S|$)(?![\.,:;]\s)',
        '*' => '(?<=\S|^)(?<!\*)\*(?!\*)',
        '_' => '(?<=\S|^)(?<!_)_(?!_)',
    );
    protected $strong_relist = array(
        ''   => '(?:(?<!\*)\*\*(?!\*)|(?<!_)__(?!_))(?=\S|$)(?![\.,:;]\s)',
        '**' => '(?<=\S|^)(?<!\*)\*\*(?!\*)',
        '__' => '(?<=\S|^)(?<!_)__(?!_)',
    );
    protected $em_strong_relist = array(
        ''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<!_)___(?!_))(?=\S|$)(?![\.,:;]\s)',
        '***' => '(?<=\S|^)(?<!\*)\*\*\*(?!\*)',
        '___' => '(?<=\S|^)(?<!_)___(?!_)',
    );
    protected $em_strong_prepared_relist;

    protected function prepareItalicsAndBold()
    {
        #
        # Prepare regular expressions for searching emphasis tokens in any
        # context.
        #
        foreach ($this->em_relist as $em => $em_re) {
            foreach ($this->strong_relist as $strong => $strong_re) {
                # Construct list of allowed token expressions.
                $token_relist = array();
                if (isset($this->em_strong_relist["$em$strong"])) {
                    $token_relist[] = $this->em_strong_relist["$em$strong"];
                }
                $token_relist[] = $em_re;
                $token_relist[] = $strong_re;

                # Construct master expression from list.
                $token_re                                      = '{(' . implode('|', $token_relist) . ')}';
                $this->em_strong_prepared_relist["$em$strong"] = $token_re;
            }
        }
    }

    protected function doItalicsAndBold($text)
    {
        $token_stack  = array('');
        $text_stack   = array('');
        $em           = '';
        $strong       = '';
        $tree_char_em = false;

        while (1) {
            #
            # Get prepared regular expression for seraching emphasis tokens
            # in current context.
            #
            $token_re = $this->em_strong_prepared_relist["$em$strong"];

            #
            # Each loop iteration search for the next emphasis token.
            # Each token is then passed to handleSpanToken.
            #
            $parts = preg_split($token_re, $text, 2, PREG_SPLIT_DELIM_CAPTURE);
            $text_stack[0] .= $parts[0];
            $token = &$parts[1];
            $text  = &$parts[2];

            if (empty($token)) {
                # Reached end of text span: empty stack without emitting.
                # any more emphasis.
                while ($token_stack[0]) {
                    $text_stack[1] .= array_shift($token_stack);
                    $text_stack[0] .= array_shift($text_stack);
                }
                break;
            }

            $token_len = strlen($token);
            if ($tree_char_em) {
                # Reached closing marker while inside a three-char emphasis.
                if (3 == $token_len) {
                    # Three-char closing marker, close em and strong.
                    array_shift($token_stack);
                    $span = array_shift($text_stack);
                    $span = $this->runSpanGamut($span);
                    $span = "<strong><em>$span</em></strong>";
                    $text_stack[0] .= $this->hashPart($span);
                    $em     = '';
                    $strong = '';
                } else {
                    # Other closing marker: close one em or strong and
                    # change current token state to match the other
                    $token_stack[0] = str_repeat($token{0}, 3 - $token_len);
                    $tag            = 2 == $token_len ? "strong" : "em";
                    $span           = $text_stack[0];
                    $span           = $this->runSpanGamut($span);
                    $span           = "<$tag>$span</$tag>";
                    $text_stack[0]  = $this->hashPart($span);
                    $$tag           = ''; # $$tag stands for $em or $strong
                }
                $tree_char_em = false;
            } else if (3 == $token_len) {
                if ($em) {
                    # Reached closing marker for both em and strong.
                    # Closing strong marker:
                    for ($i = 0; $i < 2; ++$i) {
                        $shifted_token = array_shift($token_stack);
                        $tag           = strlen($shifted_token) == 2 ? "strong" : "em";
                        $span          = array_shift($text_stack);
                        $span          = $this->runSpanGamut($span);
                        $span          = "<$tag>$span</$tag>";
                        $text_stack[0] .= $this->hashPart($span);
                        $$tag = ''; # $$tag stands for $em or $strong
                    }
                } else {
                    # Reached opening three-char emphasis marker. Push on token
                    # stack; will be handled by the special condition above.
                    $em     = $token{0};
                    $strong = "$em$em";
                    array_unshift($token_stack, $token);
                    array_unshift($text_stack, '');
                    $tree_char_em = true;
                }
            } else if (2 == $token_len) {
                if ($strong) {
                    # Unwind any dangling emphasis marker:
                    if (strlen($token_stack[0]) == 1) {
                        $text_stack[1] .= array_shift($token_stack);
                        $text_stack[0] .= array_shift($text_stack);
                    }
                    # Closing strong marker:
                    array_shift($token_stack);
                    $span = array_shift($text_stack);
                    $span = $this->runSpanGamut($span);
                    $span = "<strong>$span</strong>";
                    $text_stack[0] .= $this->hashPart($span);
                    $strong = '';
                } else {
                    array_unshift($token_stack, $token);
                    array_unshift($text_stack, '');
                    $strong = $token;
                }
            } else {
                # Here $token_len == 1
                if ($em) {
                    if (strlen($token_stack[0]) == 1) {
                        # Closing emphasis marker:
                        array_shift($token_stack);
                        $span = array_shift($text_stack);
                        $span = $this->runSpanGamut($span);
                        $span = "<em>$span</em>";
                        $text_stack[0] .= $this->hashPart($span);
                        $em = '';
                    } else {
                        $text_stack[0] .= $token;
                    }
                } else {
                    array_unshift($token_stack, $token);
                    array_unshift($text_stack, '');
                    $em = $token;
                }
            }
        }
        return $text_stack[0];
    }

    protected function doBlockQuotes($text)
    {
        $text = preg_replace_callback('/
			  (								# Wrap whole match in $1
				(?>
				  ^[ ]*>[ ]?			# ">" at the start of a line
					.+\n					# rest of the first line
				  (.+\n)*					# subsequent consecutive lines
				  \n*						# blanks
				)+
			  )
			/xm',
            array(&$this, '_doBlockQuotes_callback'), $text);

        return $text;
    }
    protected function _doBlockQuotes_callback($matches)
    {
        $bq = $matches[1];
        # trim one level of quoting - trim whitespace-only lines
        $bq = preg_replace('/^[ ]*>[ ]?|^[ ]+$/m', '', $bq);
        $bq = $this->runBlockGamut($bq); # recurse

        $bq = preg_replace('/^/m', "  ", $bq);
        # These leading spaces cause problem with <pre> content,
        # so we need to fix that:
        $bq = preg_replace_callback('{(\s*<pre>.+?</pre>)}sx',
            array(&$this, '_doBlockQuotes_callback2'), $bq);

        return "\n" . $this->hashBlock("<blockquote>\n$bq\n</blockquote>") . "\n\n";
    }
    protected function _doBlockQuotes_callback2($matches)
    {
        $pre = $matches[1];
        $pre = preg_replace('/^  /m', '', $pre);
        return $pre;
    }

    protected function formParagraphs($text)
    {
        #
        #    Params:
        #        $text - string to process with html <p> tags
        #
        # Strip leading and trailing lines:
        $text = preg_replace('/\A\n+|\n+\z/', '', $text);

        $grafs = preg_split('/\n{2,}/', $text, -1, PREG_SPLIT_NO_EMPTY);

        #
        # Wrap <p> tags and unhashify HTML blocks
        #
        foreach ($grafs as $key => $value) {
            if (!preg_match('/^B\x1A[0-9]+B$/', $value)) {
                # Is a paragraph.
                $value = $this->runSpanGamut($value);
                $value = preg_replace('/^([ ]*)/', "<p>", $value);
                $value .= "</p>";
                $grafs[$key] = $this->unhash($value);
            } else {
                # Is a block.
                # Modify elements of @grafs in-place...
                $graf  = $value;
                $block = $this->html_hashes[$graf];
                $graf  = $block;
//                if (preg_match('{
                //                    \A
                //                    (                            # $1 = <div> tag
                //                      <div  \s+
                //                      [^>]*
                //                      \b
                //                      markdown\s*=\s*  ([\'"])    #    $2 = attr quote char
                //                      1
                //                      \2
                //                      [^>]*
                //                      >
                //                    )
                //                    (                            # $3 = contents
                //                    .*
                //                    )
                //                    (</div>)                    # $4 = closing tag
                //                    \z
                //                    }xs', $block, $matches))
                //                {
                //                    list(, $div_open, , $div_content, $div_close) = $matches;
                //
                //                    # We can't call Markdown(), because that resets the hash;
                //                    # that initialization code should be pulled into its own sub, though.
                //                    $div_content = $this->hashHTMLBlocks($div_content);
                //
                //                    # Run document gamut methods on the content.
                //                    foreach ($this->document_gamut as $method => $priority) {
                //                        $div_content = $this->$method($div_content);
                //                    }
                //
                //                    $div_open = preg_replace(
                //                        '{\smarkdown\s*=\s*([\'"]).+?\1}', '', $div_open);
                //
                //                    $graf = $div_open . "\n" . $div_content . "\n" . $div_close;
                //                }
                $grafs[$key] = $graf;
            }
        }

        return implode("\n\n", $grafs);
    }

    protected function encodeAttribute($text)
    {
        #
        # Encode text for a double-quoted HTML attribute. This function
        # is *not* suitable for attributes enclosed in single quotes.
        #
        $text = $this->encodeAmpsAndAngles($text);
        $text = str_replace('"', '&quot;', $text);
        return $text;
    }

    protected function encodeAmpsAndAngles($text)
    {
        #
        # Smart processing for ampersands and angle brackets that need to
        # be encoded. Valid character entities are left alone unless the
        # no-entities mode is set.
        #
        if ($this->no_entities) {
            $text = str_replace('&', '&amp;', $text);
        } else {
            # Ampersand-encoding based entirely on Nat Irons's Amputator
            # MT plugin: <http://bumppo.net/projects/amputator/>
            $text = preg_replace('/&(?!#?[xX]?(?:[0-9a-fA-F]+|\w+);)/',
                '&amp;', $text);
        }
        # Encode remaining <'s
        $text = str_replace('<', '&lt;', $text);

        return $text;
    }

    protected function doAutoLinks($text)
    {
        $text = preg_replace_callback('{<((https?|ftp|dict):[^\'">\s]+)>}i',
            array(&$this, '_doAutoLinks_url_callback'), $text);

        # Email addresses: <address@domain.foo>
        $text = preg_replace_callback('{
			<
			(?:mailto:)?
			(
				(?:
					[-!#$%&\'*+/=?^_`.{|}~\w\x80-\xFF]+
				|
					".*?"
				)
				\@
				(?:
					[-a-z0-9\x80-\xFF]+(\.[-a-z0-9\x80-\xFF]+)*\.[a-z]+
				|
					\[[\d.a-fA-F:]+\]	# IPv4 & IPv6
				)
			)
			>
			}xi',
            array(&$this, '_doAutoLinks_email_callback'), $text);

        return $text;
    }
    protected function _doAutoLinks_url_callback($matches)
    {
        $url  = $this->encodeAttribute($matches[1]);
        $link = "<a href=\"$url\">$url</a>";
        return $this->hashPart($link);
    }
    protected function _doAutoLinks_email_callback($matches)
    {
        $address = $matches[1];
        $link    = $this->encodeEmailAddress($address);
        return $this->hashPart($link);
    }

    protected function encodeEmailAddress($addr)
    {
        #
        #    Input: an email address, e.g. "foo@example.com"
        #
        #    Output: the email address as a mailto link, with each character
        #        of the address encoded as either a decimal or hex entity, in
        #        the hopes of foiling most address harvesting spam bots. E.g.:
        #
        #      <p><a href="&#109;&#x61;&#105;&#x6c;&#116;&#x6f;&#58;&#x66;o&#111;
        #        &#x40;&#101;&#x78;&#97;&#x6d;&#112;&#x6c;&#101;&#46;&#x63;&#111;
        #        &#x6d;">&#x66;o&#111;&#x40;&#101;&#x78;&#97;&#x6d;&#112;&#x6c;
        #        &#101;&#46;&#x63;&#111;&#x6d;</a></p>
        #
        #    Based by a filter by Matthew Wickline, posted to BBEdit-Talk.
        #   With some optimizations by Milian Wolff.
        #
        $addr  = "mailto:" . $addr;
        $chars = preg_split('/(?<!^)(?!$)/', $addr);
        $seed  = (int) abs(crc32($addr) / strlen($addr)); # Deterministic seed.

        foreach ($chars as $key => $char) {
            $ord = ord($char);
            # Ignore non-ascii chars.
            if ($ord < 128) {
                $r = ($seed * (1 + $key)) % 100; # Pseudo-random function.
                # roughly 10% raw, 45% hex, 45% dec
                # '@' *must* be encoded. I insist.
                if ($r > 90 && '@' != $char) /* do nothing */;
                elseif ($r < 45) {
                    $chars[$key] = '&#x' . dechex($ord) . ';';
                } else {
                    $chars[$key] = '&#' . $ord . ';';
                }

            }
        }

        $addr = implode('', $chars);
        $text = implode('', array_slice($chars, 7)); # text without `mailto:`
        $addr = "<a href=\"$addr\">$text</a>";

        return $addr;
    }

    protected function parseSpan($str)
    {
        #
        # Take the string $str and parse it into tokens, hashing embeded HTML,
        # escaped characters and handling code spans.
        #
        $output = '';

        $span_re = '{
				(
					\\\\' . $this->escape_chars_re . '
				|
					(?<![`\\\\])
					`+						# code span marker
			' . ($this->no_markup ? '' : '
				|
					<!--    .*?     -->		# comment
				|
					<\?.*?\?> | <%.*?%>		# processing instruction
				|
					<[!$]?[-a-zA-Z0-9:_]+	# regular tags
					(?>
						\s
						(?>[^"\'>]+|"[^"]*"|\'[^\']*\')*
					)?
					>
				|
					<[-a-zA-Z0-9:_]+\s*/> # xml-style empty tag
				|
					</[-a-zA-Z0-9:_]+\s*> # closing tag
			') . '
				)
				}xs';

        while (1) {
            #
            # Each loop iteration seach for either the next tag, the next
            # openning code span marker, or the next escaped character.
            # Each token is then passed to handleSpanToken.
            #
            $parts = preg_split($span_re, $str, 2, PREG_SPLIT_DELIM_CAPTURE);

            # Create token from text preceding tag.
            if ("" != $parts[0]) {
                $output .= $parts[0];
            }

            # Check if we reach the end.
            if (isset($parts[1])) {
                $output .= $this->handleSpanToken($parts[1], $parts[2]);
                $str = $parts[2];
            } else {
                break;
            }
        }

        return $output;
    }

    protected function handleSpanToken($token, &$str)
    {
        #
        # Handle $token provided by parseSpan by determining its nature and
        # returning the corresponding value that should replace it.
        #
        switch ($token{0}) {
        case "\\":
            return $this->hashPart("&#" . ord($token{1}) . ";");
        case "`":
            # Search for end marker in remaining text.
            if (preg_match('/^(.*?[^`])' . preg_quote($token) . '(?!`)(.*)$/sm',
                $str, $matches)) {
                $str      = $matches[2];
                $codespan = $this->makeCodeSpan($matches[1]);
                return $this->hashPart($codespan);
            }
            return $token; // return as text since no ending marker found.
        default:
            return $this->hashPart($token);
        }
    }

    protected function outdent($text)
    {
        #
        # Remove one level of line-leading tabs or spaces
        #
        return preg_replace('/^(\t|[ ]{1,' . $this->tab_width . '})/m', '', $text);
    }

    # String length function for detab. `_initDetab` will create a function to
    # hanlde UTF-8 if the default function does not exist.
    protected $utf8_strlen = 'mb_strlen';

    protected function detab($text)
    {
        #
        # Replace tabs with the appropriate amount of space.
        #
        # For each line we separate the line in blocks delemited by
        # tab characters. Then we reconstruct every line by adding the
        # appropriate number of space between each blocks.

        $text = preg_replace_callback('/^.*\t.*$/m',
            array(&$this, '_detab_callback'), $text);

        return $text;
    }
    protected function _detab_callback($matches)
    {
        $line   = $matches[0];
        $strlen = $this->utf8_strlen; # strlen function for UTF-8.

        # Split in blocks.
        $blocks = explode("\t", $line);
        # Add each blocks to the line.
        $line = $blocks[0];
        unset($blocks[0]); # Do not add first block twice.
        foreach ($blocks as $block) {
            # Calculate amount of space, insert spaces, insert block.
            $amount = $this->tab_width -
            $strlen($line, 'UTF-8') % $this->tab_width;
            $line .= str_repeat(" ", $amount) . $block;
        }
        return $line;
    }
    protected function _initDetab()
    {
        #
        # Check for the availability of the function in the `utf8_strlen` property
        # (initially `mb_strlen`). If the function is not available, create a
        # function that will loosely count the number of UTF-8 characters with a
        # regular expression.
        #
        if (function_exists($this->utf8_strlen)) {
            return;
        }

        $this->utf8_strlen = create_function('$text', 'return preg_match_all(
			"/[\\\\x00-\\\\xBF]|[\\\\xC0-\\\\xFF][\\\\x80-\\\\xBF]*/",
			$text, $m);');
    }

    protected function unhash($text)
    {
        #
        # Swap back in all the tags hashed by _HashHTMLBlocks.
        #
        return preg_replace_callback('/(.)\x1A[0-9]+\1/',
            array(&$this, '_unhash_callback'), $text);
    }
    protected function _unhash_callback($matches)
    {
        return $this->html_hashes[$matches[0]];
    }

}
